The present invention relates to novel compounds which can be used in cosmetics or in pharmaceuticals, in particular in dermatology, and which make it possible in particular to obtain thickened compositions, or even gelled compositions.
Hyperbranched polymers and dendrimers are well known in the prior art.
Hyperbranched polymers are molecular constructions having a branched structure, generally around a core. Their structure generally lacks symmetry, the base units or monomers used to construct the hyperbranched polymer can be of diverse nature and their distribution is non-uniform. The branches of the polymer can be of different natures and lengths. The number of base units, or monomers, may be different depending on the different branching. While at the same time being asymmetrical, hyperbranched polymers can have: an extremely branched structure, around a core; successive generations or layers of branching; a layer of end chains.
Hyperbranched polymers are generally derived from the polycondensation of one or more monomers ABx, and B being reactive groups capable of reacting together, x being an integer greater than or equal to 2, but other preparation processes may be envisaged. Hyperbranched polymers are characterized by their degree of polymerization DP=1xe2x88x92b, b being the percentage of non-terminal functionalities in B which have not reacted with a group A. Since the condensation is not systematic, in contrast with the synthesis of dendrimers, the degree of polymerization is less than 100%. An end group T can be reacted with the hyperbranched polymer to obtain a particular functionality on the ends of chains.
Several hyperbranched polymers can be combined together, via a covalent bond or another type of bonding, by means of their end groups. Such polymers, known as bridged polymers, fall within the definition of the hyperbranched polymers according to the present invention.
Dendrimers are highly branched polymers and oligomers having a well-defined chemical structure. As a general rule, dendrimers comprise a core, a given number of generations of branches, or spindles, and end groups. The generations of spindles consist of structural units which are identical for the same generation of spindles and which may be identical or different for different generations of spindles. The generations of spindles extend radially in a geometrical progression from the core. The end groups of a dendrimer from the Nth generation are the end functional groups of the spindles of the Nth generation or end generation.
The definition of dendrimers given above includes molecules containing symmetrical branching; it also includes molecules containing non-symmetrical branching, such as, for example, dendrimers whose spindles are lysine groups, in which the branching of one generation of spindles on the preceding generation takes place on the a and c amines of lysine, which leads to a difference in the lengths of the spindles of different branching.
Dense star polymers, starburst polymers and rod-shaped dendrimers are included in the present definition of dendrimers. The molecules known as arborols and cascade molecules also fall within the definition of dendrimers according to the present invention.
Several dendrimers can be combined together, via a covalent bond or another type of bonding, by means of their end groups to give species known as bridged dendrimers or dendrimer aggregates. Such species are included in the definition of dendrimers according to the present invention.
Dendrimers can be in the form of an assembly of molecules of the same generation, which are referred to as monodisperse assemblies; they can also be in the form of assemblies of different generations, known as polydisperse assemblies. The definition of dendrimers according to the present invention includes both monodisperse and polydisperse assemblies of dendrimers.
French patent application FR 97/04085 in the name of the Applicant in particular discloses novel polymers chosen from hyperbranched polymers and dendrimers, comprising functional groups corresponding to the following formula: 
in which
Y represents an oxygen atom or an NH group,
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from amino, acylamino, carboxylic acid and ester.
These polymers find an application in particular in cosmetics and dermatology as antioxidants or reducing agents.
Now, the Applicant has found, surprisingly, that the said polymers can also be used to allow the preparation of compositions, in particular cosmetic or pharmaceutical compositions, which are thickened or even gelled.
Thus, a subject of the present invention is a compound chosen from hyperbranched polymers and dendrimers, characterized in that it comprises at least one group of formula: 
in which:
Y represents an oxygen atom or an NH group, and
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from:
amino (xe2x80x94NH2)
acylamino (xe2x80x94NHxe2x80x94COxe2x80x94R) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group,
carboxylic acid (xe2x80x94COOH),
ester (xe2x80x94COOR) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group.
Another subject of the invention is a process for preparing the above compounds, in which a polymer is oxidized, this polymer being chosen from hyper-branched polymers and dendrimers comprising at least one group of formula (II): 
Another subject of the invention is the use of at least one compound as above, as a thickener or gelling agent, in particular in a cosmetic or pharmaceutical composition also comprising a cosmetically or pharmaceutically acceptable medium.
Another subject of the invention is a cosmetic or pharmaceutical composition comprising, in a cosmetically or pharmaceutically acceptable medium, at least one compound as defined above.
Another subject is the use of at least one polymer chosen from hyperbranched polymers and dendrimers comprising at least one group of formula (II), for the preparation of a composition comprising at least one compound as defined above.
The prior art discloses a certain number of common gelling agents or thickeners which can be used to modify the viscosity of compositions, in particular cosmetics. Mention may thus be made of algal extracts such as agar-agar, carrageenans and alginates; gums; seed extracts, plant exudates or microorganism exudates, and cellulose derivatives; fruit extracts such as pectins; gelling agents of animal origin such as gelatin, caseinates or water-soluble gelling synthetic polymers such as crosslinked polyacrylic acids.
However, these gelling agents have certain drawbacks. Specifically, the common gelling agents give gels or thickened media as soon as they are introduced into the said medium. They must thus necessarily be introduced into the medium before it is applied to the intended support.
Now, it has been found that by using the compounds according to the invention or a composition comprising them, it is possible to form the gel when desired, and in particular in situ, i.e. after the composition has been applied to the support.
Thus, it is possible to form the said gel before it has been packaged, and thus to have available a ready-to-apply gelled composition. In this case, the compounds according to the invention are used like common gelling agents.
However, it is also possible to prepare a composition which is not gelled because it is not oxidized, to package it in this form and to carry out the oxidation, and thus the gelation, only when the composition is applied to the support, for example by oxidation in the open air. This may be advantageous in particular in the case of haircare uses, such as styling gels or hair-colouring compositions.
Thus, the invention provides a system for gelling the composition before, during or after it has been applied to the support.
Another advantage of the invention lies in the tact that, in certain cases, it may be necessary to store separately two liquid solutions which need to be mixed together at the time of application, the viscosity of the resulting mixture needing to be increased before application. This is the case in particular for certain hair-colouring products. The compounds according to the invention allows these requirements to be satisfied.
The compounds which are the subject of the invention are thus chosen from hyperbranched polymers and dendrimers, and comprise at least one group of formula (I): 
in which:
Y represents O or NH,
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from:
amino (xe2x80x94NH2) optionally in the form of a salt of an inorganic or organic acid,
acylamino (xe2x80x94NHxe2x80x94COR) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group,
carboxylic acid (xe2x80x94COOH),
ester (xe2x80x94COOR) in which R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group.
Preferably, the compound according to the invention is chosen from hyperbranched polymers, and in particular polyethyleneimine, comprising at least one group of formula (I).
Preferably, Y represents an oxygen atom.
Preferably, the hetero atoms are chosen from oxygen and nitrogen (O and N).
Preferably, A is a methylene, ethylene, propylene, methylpropylene, ethylpropylene, tetramethylene, pentamethylene, hexamethylene, phenylene or phenyldiyl group.
Advantageously, A represents a radical corresponding to one of the formulae (a) to (d) below:
(a) xe2x80x94CHR1xe2x80x94CHR2xe2x80x94CHR3xe2x80x94
(b) xe2x80x94CHRxe2x80x21xe2x80x94CHRxe2x80x22xe2x80x94CHRxe2x80x23xe2x80x94CHRxe2x80x24xe2x80x94
(d) xe2x80x94(CHRxe2x80x2xe2x80x31)kxe2x80x94(CHRxe2x80x2xe2x80x32)xe2x80x94CH(CO2H)xe2x80x94NHxe2x80x94
in which
R1, R2, R3, Rxe2x80x21, Rxe2x80x22, Rxe2x80x23 and Rxe2x80x24, Rxe2x80x2xe2x80x31 and Rxe2x80x2xe2x80x32, which may be identical or different, represent: a hydrogen atom; a linear, branched or cyclic, saturated or unsaturated C1-C6 alkyl radical; an amino (xe2x80x94NH2) radical; a carboxylic acid (xe2x80x94COOH) radical; a C1-C10 alkylamino radical; a C1-C10 acylamino radical;
Rxe2x80x31, Rxe2x80x32, Rxe2x80x33 and Rxe2x80x34, which may be identical or different, represent: a hydrogen atom; a linear or branched, saturated or unsaturated C1-C4 alkyl radical, the arrows indicating the positions of the substitutions;
k is an integer, preferably 0 or 1.
Preferably, A is chosen from the following groups:
xe2x80x94CH2xe2x80x94CH(CO2H)xe2x80x94NHxe2x80x94; xe2x80x94(CH2)2xe2x80x94(CH3CONH)CHxe2x80x94; xe2x80x94(CH2)3xe2x80x94 and xe2x80x94CH2xe2x80x94CH(NHxe2x80x94COxe2x80x94CH3)xe2x80x94.
The compounds according to the invention can be obtained in particular by oxidation of the polymers described in patent application FR 97/04085, the content of which is incorporated by way of reference, and which are chosen from hyperbranched polymers and dendrimers, comprising functional groups corresponding to formula (II): 
in which:
Y represents O or NH,
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkanediyl group, this group optionally being interrupted with one or more hetero atoms and/or substituted with a function chosen from amino, acylamino, carboxylic acid and ester.
The oxidation can be carried out by any known means, for example in air or using a common oxidizing agent such as hydrogen peroxide.
The oxidation step allows the formation of intramolecular and intermolecular disulphide bridges, starting with thiol functions, according to the scheme below: 
The formation of disulphide bridges brings about a xe2x80x9cpseudo-crosslinkingxe2x80x9d of the starting compounds A, which is reflected, depending on the experimental conditions, in thickening/gelation of the medium, due to the formation of the compounds B. A gel comprising the compounds B is thus obtained directly.
The oxidation step is preferably carried out in the presence of water, for example in aqueous or aqueous-alcoholic medium.
It is thus possible to obtain gels which may be, preferably, aqueous gels or aqueous-alcoholic gels containing only water or an alcohol/water mixture, for example ethanol/water, one or more compounds B according to the invention and optionally starting compounds A that have not reacted, when the oxidation is only partially performed.
Moreover, it has been found that it is possible to incorporate water-soluble or water-insoluble additives into the aqueous or aqueous-alcoholic medium while at the same time retaining the possibility of obtaining a composition of adequate viscosity.
Among the additives which can be incorporated, mention may be made of water-soluble dyes such as fluorescein; water-soluble cosmetic or pharmaceutical active agents; water-insoluble products which have optical properties such as phosphorescence or fluorescence; pigments; fillers; sunscreens; water-insoluble cosmetic or pharmaceutical active agents.
It has moreover been found that the solid additives, pigment particles or fillers, for example, were fully dispersed homogeneously in the gel; when the viscosity of the mixture is sufficient, no decantation or release of the said particles is observed.
It is known that the properties of the gels obtained depend on the oxidation conditions, in particular the concentration of starting thiol-containing polymer, the number of thiol functions in the said thiol-containing polymer, the molar mass of the said polymer and the pH of the aqueous/aqueous-alcoholic medium before oxidation.
Thus, for example, for a poly(ethyleneimine) of given molar mass (molar mass before grafting the thiol functions), the thiol grafts being identical, it has been found that the higher the number of grafts, the more the compounds will gel at low concentration and at more acidic pH.
A thickened solution or a gel is thus obtained, which can preferably have a viscosity of between 10xe2x88x922 and 107 Paxc2x7s, in particular between 10 and 107 Paxc2x7s and, for example, between 104 and 106 Paxc2x7s, and which can be used, in its native form, as a cosmetic or pharmaceutical composition, or incorporated into a composition, in particular a cosmetic or pharmaceutical composition.
Depending on the oxidation conditions, it is possible for the fully oxidized mixture to remain liquid with a very small increase in viscosity (the disulphides are water-soluble at low concentration). In this case, the medium can be concentrated until a very thickened or gelled solution is obtained, depending on the use envisaged.
It is also possible to totally or partially extract the water present in the said gel, for example by drying under vacuum. The dried product thus obtained, which is generally hygroscopic, once again gives a gel when it is put back in water under suitable conditions.
When solid additives, for example such as pigment particles, are added to the medium before the oxidation step and when the gel obtained is dried, it is found that, when the dried product is rehydrated by adding water and/or alcohol, a gel having the initial characteristics is once again obtained, in particular without any xe2x80x9creleasexe2x80x9d of the said solid particles being observed.
When the gel comprising the compounds according to the invention is intended to be used in a cosmetic or pharmaceutical composition, the said composition moreover comprises a cosmetically or pharmaceutically acceptable medium.
The said cosmetic or pharmaceutical composition can be in any form which is suitable for topical application, in particular in the form of aqueous or aqueous-alcoholic gels; in the form of water-in-oil, oil-in-water or multiple emulsions, of more or less thickened liquid consistency, such as a milk or cream; sprays or aerosol mousses; sticks or tubes; solutions or liquid dispersions.
A person skilled in the art knows how to prepare these compositions according to the usual methods, on the basis of his or her general knowledge.
In particular, these compositions can contain adjuvants usually used in the cosmetics or pharmaceuticals fields, such as oils, waxes or other common fatty substances; surfactants; moisturizers; emollients; sunscreens; hydrophilic or lipophilic active agents such as ceramides; free-radical scavengers; polymers; proteins; bactericides; sequestering agents; antidandruff agents; antioxidants; preserving agents; basifying or acidifying agents; fragrances; fillers; dyestuffs; cosmetic or pharmaceutical active agents. The amounts of these various adjuvants are those conventionally used in the fields under consideration and can readily be determined by a person skilled in the art.
Needless to say, a person skilled in the art will take care to select this or these optional additional adjuvant(s), and/or the amount thereof, such that the advantageous properties of the composition according to the invention are not, or are not substantially, adversely affected by the envisaged addition.
The compositions according to the invention are, for example, lotions, milks or creams for skincare or haircare; make-up-removing creams, lotions or milks; foundation bases; antisun or after-sun lotions, milks or creams; artificial tanning lotions, milks or creams; shaving creams or foams; aftershave lotions; body hygiene compositions such as deodorant sticks or creams; shampoos; hair products for maintaining the hairstyle or for shaping the hair such as styling gels; hair-colouring products; lipsticks; mascaras or eyeliners which may be for treatment purposes; nail varnishes or nailcare products.